1. Field of the Invention
This invention relates to insulated piping, and more particularly to a method of applying fittings to insulated piping.
2. Prior Art
Insulated piping has found widespread industrial and commercial applications in recent years. A standard form of such insulated piping consists of individual lengths of factory insulated pipe assembly. These lengths consist of one or more inner pipes for carrying the media to be piped, an envelope of insulation material around the inner pipe and a shroud of protective material around the envelope of insulation. Standard piping today may include copper, steel or aluminum inner pipes, a rigid, closed or open celled foam insulation and an outer shell of plastic, such as PVC, polyethylene, or the like. These materials are assembled together in a factory by methods such as that disclosed in U.S. Pat. No. 3,793,411, issued to Lawrence J. Stonitch and Richard W. Stonitch on Feb. 19, 1974, the teachings of which are herein specifically incorporated by reference.
Factory completed insulated lengths are then field installed in appropriate piping configurations. In order to facilitate field insulation, such lengths are normally sent from the factory with inner piping portions projecting beyond the ends of the insulation envelope and protective outer shroud. Where lengths of piping are to be coaxially coupled with other lengths, various coupling arrangements have been suggested, such as, those shown in U.S. Pat. Nos. 4,084,842 and 4,221,405, issued to Lawrence J. Stonitch and Richard W. Stonitch, respectively, on Apr. 18, 1978 and Sept. 9, 1980, the teachings of which are also herein incorporated by reference.
One standard known method of connecting coaxial lengths together involves welding the ends of the inner pipes to one another, enclosing the gap between the ends of the insulation envelopes and shroud ends of the welded together pipe lengths, pouring foam into the interior of the enclosure and thereafter wrapping the foamed area either around the enclosure or after removal of the enclosure. The wrapping can be accomplished either by protective tape or by use of heat shrink materials.
While such methods work adequately for coaxial connections, they are not readily accepted for angle connections, including right angle connections, T-connections, 60.degree. angle connections, etc. Such connections are commonly referred to in the trade under the generic term "fitting". In such angle connections, it is necessary to interpose a preformed pipe member having the desired angular shape. Such pipe member or "fitting" must then be welded to each of the straight lengths of insulated piping. This provides a relatively long span between the ends of the factory insulated pipe lengths. This span must be then field insulated. Heretofore, this has done in the field in the same manner. That is, an enclosure or mold form shaped to define the area around the fitting and between the ends of the shrouds of the premanufactured lengths would be clamped in place and attached to the length shrouds after welding up the fitting. Thereafter, the area interior of the mold and around the inner pipes and fitting would be filled with insulating foam, the enclosure would be removed and the resultant area tape wrapped to provide protection to the insulation. Such field joints, particularly those which are tape wrapped, are undesirable because they do not offer adequate protection to the insulation envelope or jacket at the high stress area of the fitting. It is preferred, in the trade, to provide a stronger protection at fittings than can effectively be provided by tape wrapping.
In order to provide the desired protection, it has known to pre-insulate fittings in the factory in substantially the same manner in which the straight lengths are preinsulated. However, since standard fittings are relatively short, in order to provide the necessary projection beyond the actual curve, it has been standard practice to weld onto the end of the fitting extension pipes prior to insulating in the factory. The fitting with the extension pipes is then assembled into a standard material shroud having a conforming shape to the fitting and the resultant assembly is then factory insulated. The extensions then project beyond the ends of the fitting shroud and beyond the ends of the factory insulation and connections are then made to the straight lengths in this standard manner in the field. This practice is a decided advantage over the field insulation of fittings in that better control of insulation density and quality can be obtained and the resultant angle joint is provided with a protective hard shroud. Such methods, however, are expensive in that they require costly factory sourced fittings which must be matched on site to the needs of the particular installation.
It would therefore be a definite advance in the art to develop a method of field installation of insulated pipe joints which provides the advantages of a protective hard shroud around the joint fitting while minimizing the number of welds necessary and avoiding the expense of using pre-insulated fittings.